Adult survivors of childhood cancer are at seven times the risk of dying from cardiovascular disease compared to the general population. The increased risk is thought to be the result of the therapies used to treat the cancer such as chemotherapy and radiation. These therapies likely cause damage to the endothelial cells, which line the arterial wall and, when function properly, offer protection from atherosclerosis. Young adult survivors of childhood ALL have reduced endothelial function, or endothelial dysfunction, compared to healthy controls. Endothelial dysfunction is considered an early manifestation of atherosclerosis and therefore is an ideal target of therapy in order to reduce the risk of cardiovascular disease. Interventions that improve endothelial function in young adult survivors of childhood cancer may be beneficial in terms of mitigating the medium- and long-term risk of developing this chronic disease.